This section provides background information related to the present disclosure which is not necessarily prior art. Unless specified otherwise, it is appreciated that throughout the description, directional terms, such as upper side/lower side, over/below and so on are defined with respect to the directions in the accompanying drawings.
FIG. 1 is a view showing an exemplary embodiment of a semiconductor light emitting chip in the prior art.
In this semiconductor light emitting chip, there is provided a growth substrate 10 (e.g., a sapphire substrate), and layers including a buffer layer 20, a first semiconductor layer 30 having a first conductivity (e.g., an n-type GaN layer), an active layer 40 adapted to generate light by electron-hole recombination (e.g., INGaN/(In)GaN MQWs) and a second semiconductor layer 50 having a second conductivity different from the first conductivity (e.g., a p-type GaN layer) are deposited over the substrate in the order mentioned. A light-transmitting conductive film 60 for current spreading is then formed on the second semiconductor layer, followed by an electrode 70 serving as a bonding pad formed on the light-transmitting conductive film, and an electrode 80 (e.g., a Cr/Ni/Au stacked metallic pad) serving as a bonding pad is formed on an etch-exposed portion of the first semiconductor layer 30. This particular type of the semiconductor light emitting chip as in FIG. 1 is called a lateral chip. Here, the side of the growth substrate 10 serves as a mounting face during electrical connections to outside.
FIG. 2 is a view showing another exemplary embodiment of a semiconductor light emitting chip disclosed in U.S. Pat. No. 7,262,436. For convenience of description, different reference numerals are used for some parts.
In this semiconductor light emitting chip, there is provided a growth substrate 10, and layers including a first semiconductor layer 30 having a first conductivity, an active layer 40 adapted to generate light by electron-hole recombination and a second semiconductor layer 50 having a second conductivity different from the first conductivity are deposited over the substrate in the order mentioned. Three-layered electrode films 90, 91 and 92 adapted to reflect light towards the growth substrate 10 are then formed on the second semiconductor layer, in which first electrode film 90 can be a reflective Ag film, second electrode film 91 can be a Ni diffusion barrier, and third electrode film 92 can be an Au bonding layer. Further, an electrode 80 serving as a bonding pad is formed on an etch-exposed portion of the first semiconductor layer 30. Here, the side of the electrode film 92 serves as a mounting face during electrical connections to outside. This particular type of the semiconductor light emitting chip as in FIG. 2 is called a flip chip. While the electrode 80 formed on the first semiconductor layer 30 is placed at a lower height level than the electrode films 90, 91 and 92 formed on the second semiconductor layer in the case of the flip chip shown in FIG. 2, it may be formed at the same height level as the electrode films. Here, height levels are given with respect to the growth substrate 10.
FIG. 3 is a view showing one exemplary embodiment of a semiconductor light emitting device 100 in the prior art.
The semiconductor light emitting device 100 is provided with lead frames 110 and 120, a mold 130, and a vertical type light-emitting chip 150 in a cavity 140 which is filled with an encapsulating member 170 containing a wavelength converting material 160. The lower face of the vertical type light-emitting chip 150 is directly electrically connected to the lead frame 110, and the upper face thereof is electrically connected to the lead frame 120. A portion of the light coming out of the vertical type light-emitting chip 150 excites the wavelength converting material 160 such that light of a different color is generated, and these two different lights are mixed to produce white light. For instance, the semiconductor light emitting chip 150 generates blue light, and the wavelength converting material 160 is excited to generate yellow light. Then these blue and yellow lights can be mixed to produce white light. Even though the semiconductor light emitting device shown in FIG. 3 is produced using a vertical type light emitting chip 150, other types of the semiconductor light emitting devices similar to one in FIG. 3 may be produced using the semiconductor light emitting chips illustrated in FIG. 1 and FIG. 2. However, as for the semiconductor light emitting device 100 described in FIG. 3, a bonded state should be established between the semiconductor light emitting chip 150 and the lead frames 110 and 120. Particularly, in case of using the flip chip shown in FIG. 2, it is very likely that light intensity from the flip chip may be lost due to a bonding material (e.g., solder paste) used for bonding the flip chip to the lead frames 110 and 120. Moreover, a properly bonded state may not be established between the semiconductor light emitting chip 150 and the lead frames 110 and 120 because of heat that is generated during the SMT process for bonding the semiconductor light emitting device 100 to an external substrate (e.g., a PCB substrate, a sub-mount, etc.)
In this regard, the present disclosure is directed to provide a semiconductor light emitting device in which electrodes of a semiconductor light emitting chip used in a semiconductor light emitting device are bonded directly to an external substrate. More particularly, the present disclosure is directed to provide a semiconductor light emitting device using a flip chip, in which no bonding between lead frames and the flip chip is required such that no light intensity from the flip chip would be lost due to bonding between the lead frames and the flip chip despite the use of the flip chip.